1. Field of the Invention
The present invention is generally directed to a relay drive for a polarized relay, and more particularly, to a relay drive having an armature movable in at least one working air gap provided between two pole faces of a split yoke, at least one permanent magnet and a coil permeated by parts of the yoke or a core connected directly therewith.
2. Description of the Prior Art
A wide variety of devices employ relays for remote switching and control, protection of electrical devices and systems, and in digital computers. Many types of relay drives are known. East German Patent No. 73,359 discloses a relay having a core surrounded by a coil and yoke parts attached to the end surfaces of the core thereby providing a working air gap. An unpolarized armature is mounted on a guide plate which abuts a pole area and on the other pole area a permanent magnet is placed. The armature extends beyond the pole area connected with the permanent magnet and abuts thereon in one of its two end positions so that the armature forms a magnetic short circuit in one of its two end positions.
The relay according to East German Patent No. 73,359, however, has a low sensitivity because in order to lift the armature from its position short-circuiting the permanent magnet, the coil must produce an appropriate magnetization.
Many types of relay structures are also known. European Patent No. A1-157 029 discloses a relay in which the yoke has two interconnected laterally pulled-up lugs and a reed that locks together between them. European Patent No. A2-130 423 discloses a relay having a yoke in the shape of an E with the coil placed on the central limb of the yoke. The relays according to European Patents A1-157-029 and A2-130 423 suffer from the disadvantage that the danger of armature chatter is always present due to the size and mass of the armature.
Polarized relays can be formed from neutral relays by bending a yoke part and the armature present in a neutral relay of an appropriate type and inserting another yoke part and a permanent magnet. This is of significance only in the production of the relay parts and the assembly thereof. The prior art construction in no way permits a change in the type of polarized relay, i.e. from a monostable relay to a bistable relay.